As is well known, “steam floods” or “steam drives” are commonly used to recover heavy hydrocarbons, e.g. heavy, viscous oil, from subterranean reservoirs. In a typical steam flood, steam is injected through one or more injection wells. The steam flows through the formation towards one or more production wells, which are separate from the injection well(s).
Typically, the temperature of the steam in the average is around 500° F. (260° C.), and can sometimes even be higher than 600° F. (315° C.). The steam heats the heavy hydrocarbons and other formation fluids, thereby lowering the viscosity of the oil, which reduces their resistance to flow. In addition, the steam provides an additional driving force to increase the flow of oil and other formation fluids toward the production well(s) where the fluids can be produced to the surface.
The wells used in steam floods, both the injection wells and the production wells, are completed either “open-hole” or cased hole and then “gravel packed” to control the flow of sand and/or other particulate material from the formation into the wellbore. In a typical gravel pack completion, a sand control screen, slotted liner or the like, is positioned in the wellbore adjacent the injection or production interval and is surrounded by “gravel” which, in turn, is sized to block the flow of formation particulate material therethrough while allowing the flow of fluids between the formation and the screen.
One of the most serious problems encountered in steam floods or drives is the early breakthrough of steam at the production well. The steam tends to dissolve carbonates and silica materials in the rocky material of subterranean formations, which tends to increase the pH of the steam to the range of about 11-13. The high temperature and the high pH of the steam tend to literally dissolve the gravel sand, which in turn creates void spaces within the gravel pack in the annulus around the production well. In many cases, these void spaces become “hot spots” as the least resistant flow paths. Formation fines or sand also tends to produce along with the production which causes erosion and cut through the gravel pack screens. Pulling the screens and re-gravel packing the well are not favorable options.
U.S. Pat. No. 4,323,124 issued Apr. 6, 1982 having for named inventor Philip G. Swan and assigned to Sigma Chemical Corp. describes in the Abstract thereof a method of inhibiting dissolution of the gravel pack and/or erosion of the formation standstone in a well bore subject to water or steam injection. The method includes the addition of a material to the surface of the gravel or formation which is capable of adhering to such surfaces and forming a tenacious water-repellent film. The film is monomolecular and hydrophobic. The active ingredient in the chemical treatment is commercial soybean lecithin. The material is added to the surfaces by injecting a liquid solution of the chemical down the annulus of the well during steaming and/or physically precoating the gravel pack by soaking it in a liquid solution of the chemical.
U.S. Pat. No. 4,427,069 issued Jan. 24, 1984 having for named inventor Robert H. Friedman and assigned to Getty Oil Company describes in the Abstract thereof that methods are provided for selectively consolidating sand grains within a subterranean formation. First an acidic salt catalyst such as ZnCl2 is injected into the subterranean formation, wherein the acidic salt catalyst is adsorbed to the surface of the sand grains. Next a polymerizable resin composition such as furfuryl alcohol oligomer is introduced into the well formation. Polymerization of the resin occurs upon exposure to the elevated well temperatures and contact with the acid salt catalyst adsorbed to the sand grains. The polymerized resin serves to consolidate the surfaces of the sand grains while retaining permeability through the pore spaces. An ester of a weak organic acid is included with the resin compositions to control the extent of a polymerization by consuming the water by-product formed during the polymerization reaction.
U.S. Pat. No. 4,428,427 issued Jan. 31, 1984 having for named inventor Robert H. Friedman and assigned to Getty Oil Company describes in the Abstract thereof that sand or similar material coated with a polymerizable resin and catalyst is suspended in a viscous fluid carrier. Such a composition is useful for introduction into a wellbore to effect gravel packing of washed-out cavities surrounding the wellbore. The viscous fluid carrier serves to maintain a heterogeneous suspension of sand as the composition is flowed down through the wellbore, so as to prevent premature settling of sand into gradient layers and voids. The fluid carrier includes a polymeric thickener and a small concentration of viscosity-enhancing agent, such as a dye. The viscosity-enhancing agent is effective to alter the configuration of polymeric thickener so as to enhance the viscosity imparted thereby. The sand or gravel included in the gravel packing composition is coated with a polymerizable resin and latent catalyst. At formation condition, the resin polymerizes and links together adjacent sand particles thereby forming a permeable consolidated structure which serves to reestablish washed-out cavities surrounding a borehole are disclosed.
U.S. Pat. No. 4,895,207 issued Jan. 23, 1990 having for named inventors Robert H. Friedman and Billy W. Surles and assigned to Texaco, Inc. describes in the Abstract thereof a fluid and method for suspending resin coated sand in order to place the sand adjacent to a production well for the purpose of forming permeable consolidated gravel pack. The fluid contains a viscosifying amount of hydroxyethylcellulose, sufficient fluorescent dye to increase the viscosity of the fluid, sodium chloride, and an acid forming component such as phthalic anhydride or succinic anhydride. As fluid containing the resin coated gravel particles is pumped down the injection string and positioned where it is desired to form the consolidated gravel pack, the acid forming material slowly reacts with water to form an acid, reducing the pH of the fluid, and thereby reducing the viscosity of the carrier fluid which facilitates the resin coated sand grains coning together in order to form the desired gravel pack.
U.S. Pat. No. 4,938,287 issued Jul. 3, 1990 having for named inventors Robert H. Friedman; Billy W. Surles; and Phillip D. Fader and assigned to Texas, Inc. describes in the Abstract thereof methods for selectively consolidating naturally occurring mineral grains such as sand grains within a subterranean formation to form a fluid permeable barrier, which restrains the movement of said particles when oil passes through the barrier. When applied to formations in which at least a portion of the sand grains are coated with a viscous oily residue of crude oil, or where the pore spaces between the sand grains contain excessive quantities of water, either of which interfere with the polymerization of the polymerizable monomer employed for said consolidation, a preflush is utilized which functions both to remove the oily residue from the said grains and to remove water from the pore spaces of the formation adjacent to the wellbore. The preflush is preferably an ester such as ethyl acetate or butyl acetate in an amount sufficient to occupy substantially all of the pore space of the formation into which the polymerizable component employed for sand consolidation are subsequently injected. In one preferred embodiment an acid catalyst such as sulfuric acid is added to the preflush. After injection of the preflush, the sand consolidation fluid usually containing a monomer or oligomer of furfuryl alcohol is injected, either mixed with steam to form a mulitphase treating fluid or injected as a liquid phase into the formation.
U.S. Pat. No. 5,010,953 issued Apr. 30, 1991 having for named inventors Robert H. Friedman and Billy W. Surles and assigned to Texaco, Inc. describes in the Abstract thereof methods for selectively consolidating naturally occurring mineral grains such as sand grains within a subterranean formation to form a fluid permeable barrier, which restrains the movement of sand particles when oil passes through the barrier. A sand consolidation fluid usually containing a monomer or oligomer of furfuryl alcohol is injected, either mixed with steam to form a multiphase treating fluid or injected as a liquid phase into the formation. The fluid contains an acid catalyst and an ester and an effective amount of a swelling polymer to reduce shrinkage of the furfuryl alcohol when it polymerizes in the formation. A preferred swelling polymer is a copolymer of starch and an acrylamides or acrylates.
U.S. Pat. No. 5,199,490 issued Apr. 6, 1993 having for named inventors Billy W. Surles, Philip D. Fader, and Carlos W. Pardo and assigned to Texaco, Inc. describes in the Abstract thereof processes for treating a subterranean formation to improve the permeability distribution by reducing the permeability in high permeability zones, so fluids injected for oil recovery purposes will sweep more uniformly through the formation. The processes involve injecting a polymerizable compound, preferably a monomer or oligomer of furfuryl alcohol, together with a diluent, preferably an ester such as butyl acetate, and a suitable acid catalyst for the formation conditions, generally toluenesulfonic acid. The fluid may be injected in a liquid phase or mixed with steam or non-condensable gas to form an aerosol, which is injected then into the formation prior to the injection of the oil recovery fluid, which may be water, surfactant fluid, polymer fluid, or steam.
U.S. Pat. No. 5,240,075 issued Aug. 31, 1993 having for named inventors Darryl N. Burrows and Paul S. Northrop and assigned to Mobil Oil Co. disclosed in the Abstract thereof a method and apparatus for treating steam which is to be injected into a formation through a gravel pack well completion by preventing dissolution and removal of silica from the gravel pack. The steam is flowed through a treatment vessel which is filled with a silica-containing material, e.g. sand, where it dissolves silica from the sane prior to injection through the gravel pack. Since the treated steam is already substantially saturated with silica, it will not dissolve any substantial amounts of silica from the gravel pack. The treatment vessel can also be heated during treatment, if desired.
U.S. Pat. No. 5,551,513 issued Sep. 3, 1996 having for named inventors Billy W. Surles and Howard L. McKinzie and assigned to Texaco Inc. describes in the Abstract thereof an improvement in a prepacked well screen assembly which includes coating the granular material in the filter medium with a resin system including an oligomer of furfuryl alcohol, a catalyst including an oil soluble, slightly water soluble organic acid, and an ester of a weak organic acid to consume water produced by the polymerization of the resin.
U.S. Pat. No. 6,632,778 issued Oct. 14, 2003 having for named inventors Joseph A. Ayoub, John P. Crawshaw, and Paul W. Way assigned to Schlumberger Technology Corp. describes in the Abstract thereof a fluid that is useful in consolidating a formation without the use of a gravel pack and screen. In particular, the fluid is useful in consolidating heterogeneous formations where the permeability is not uniform over-the total formation thickness, e.g. a formation having at least a first layer and a second layer, wherein the permeability of the first layer is greater than that of the second layer. The fluid comprises at least one of a resin, a curing agent, and a surfactant, wherein the fluid is self-diverting. Optionally, a catalyst or other additives, such as an oil wetting agent, can be used. Fluids of the present invention are self-diverting, i.e. in a formation comprising at least a first layer and a second layer, wherein the first layer has a higher permeability than the second layer, the depth of penetration of the fluid into the second layer will be greater than that predicted from the permeability ratio (the ratio of the permeability of the first layer to that of the second layer). Self-diversion can be achieved by structuring the fluid by incorporation of another phase, either liquid or gas, or by using an additive in the fluid. Also disclosed are methods for using such a fluid to consolidate a formation, especially a heterogeneous formation.
Thus, there is a continuing and long-felt need for solutions to the problem of early breakthrough of steam at a production well.